Abstract
Purpose :
To determine whether the shorter acting sevoflurane will provide an alternative to propofol for visual electrophysiology testing, we compared electroretinograms (ERGs) and visual evoked potentials (VEPs) recorded in pediatric patients with Sevoflurane gas versus propofol infusions for general anesthesia.
Methods :
Study cohort was comprised of paediatric patients that underwent general anesthesia for an eye examination including an ERG and/or VEP. General anesthesia was initiated with sevoflurane, and a protocol for simultaneous ERG and VEP recording was initiated once a 1.0 minimum alveolar concentration (MAC) of sevoflurane was achieved for five minutes. Repeat recordings, were initiated with a propofol infusion at 150-250 mcg/kg/min when the sevoflurane concentration decreased to 0.2 MAC. Stimuli were presented sequentially to each eye and included ISCEV standard light-adapted flash and standard checkerboard pattern reversal. The amplitude and implicit times of each of the key voltage peaks from the ERG and VEP waveforms were compared between the two anesthetic agents.
Results :
Flash ERGs showed close agreement between anesthetics in a- and b-wave amplitudes and implicit times. However, the photopic negative response (PhNR) following the b-wave was larger with propofol than with servofluorine (14.9 vs 9.77 µV below baseline, p<0.05). PERGs showed no differences in the P50 or N95 waveforms. Flash VEPs were recordable with both anesthetics in 8 eyes, with neither in 6 eyes and in 4 eyes with one drug only. VEP amplitudes did not differ between anesthetics but both the P1 and N2 peaks were earlier with propofol (p<0.05).
Conclusions :
Although the sample is small, the within session study design controlled for multiple confounding factors such as ocular dimensions, pigmentation, age and clinical condition. We found no evidence for differential effects of servofluorine and propofol on the retinal generators of ERGs. With servofluorine, smaller PhNRs and delayed VEPs suggest a differential effect on retinal ganglion cells and on neurons of the primary visual pathways respectively.
This is a 2020 ARVO Annual Meeting abstract.